Semiconductor device

ABSTRACT

A semiconductor device including a substrate; a chip on which a surface electrode is formed; and a lead. The lead includes a first electrode connecting portion disposed on the surface electrode and electrically connected to the surface electrode of the chip via a conductive bonding material; a second electrode connecting portion electrically connected to an electrode portion of a wiring pattern. A lead connected to the first electrode connecting portion and the second electrode connecting portion. The lead further has a thermal shrinking stress equalizing structure on a portion of an outer periphery of the first electrode connecting portion. The lead is configured to make a thermal shrinking stress applied to a conductive bonding material between the first electrode connecting portion and the surface electrode equal.

RELATED APPLICATIONS

The present application is a National Phase of International Application Number PCT/JP2019/015295, filed Apr. 8, 2019.

TECHNICAL FIELD

The present invention relates to a semiconductor device.

BACKGROUND ART

Conventionally, there has been known a semiconductor device where a chip and a lead are bonded to each other via a conductive bonding material (solder) (see patent document 1, for example).

As shown in FIG. 7A, the conventional semiconductor device 900 includes: a substrate 910 which has a front surface on which a wiring pattern is formed; a chip 920 which is mounted on the substrate 910 and has a surface electrode 922 formed on a surface of the chip 920 on a side opposite to a substrate 910 side; and a lead 930. The lead 930 has: a first electrode connecting portion 932 which is disposed on the surface electrode 922 and is electrically connected to the surface electrode 922 of the chip 920 via a solder 950 which is used as a conductive bonding material (see FIG. 7B); a second electrode connecting portion 934 which is connected to an electrode portion of the wiring pattern; and a current conductive portion 936 which is connected to the first electrode connecting portion 932 and the second electrode connecting portion 934 and forms a current conductive path between the first electrode connecting portion 932 and the second electrode connecting portion 934.

The conventional semiconductor device 900 includes the lead 930 having: the first electrode connecting portion 932 which is disposed on the surface electrode 922 and is electrically connected to the surface electrode 922 of the chip 920 via the solder 950; the second electrode connecting portion 934 which is connected to the electrode portion of the wiring pattern; and the current conductive portion 936 which is connected to the first electrode connecting portion 932 and the second electrode connecting portion 934 and forms the current conductive path between the first electrode connecting portion 932 and the second electrode connecting portion 934. Accordingly, such a conventional semiconductor device 900 is a semiconductor device which allows a conduction of a large current compared to a case where a conductive wire or the like is used for forming a current conductive path.

PRIOR ART DOCUMENT

Patent document

-   Patent document 1: JP 2015-176916 A

SUMMARY OF INVENTION Problem to be Solved by the Invention

However, in the conventional semiconductor device 900, in bonding the chip 920 and the lead 930 to each other by the solder 950 by heating the substrate 910, the chip 920 and the lead 930, there is a possibility that a thermal shrinking stress which is applied to the solder 950 differs depending on portions of the solder 950. For example, as shown in FIG. 7B, on a current conductive portion 936 side of the first electrode connecting portion 932, the solder 950 spreads by wetting along a surface of the lead 930 on a chip 920 side. On the other hand, on a side of the lead 930 opposite to a current conductive portion 936 side, not only the solder 950 spreads by wetting on a surface of the lead 930 on a chip 920 side, but also the solder 950 creeps along a side surface of the lead 930 (a side surface of the first electrode connecting portion 932). Accordingly, a surface area of the solder 950 which is brought into contact with the lead 930 (including a front surface and side surfaces of the lead 930) differs between one side (a current conductive portion 936 side) of the first electrode connecting portion 932 and a side of the first electrode connecting portion 932 opposite to the above-mentioned one side and hence, a thermal shrinking stress applied to the solder 950 between the chip 920 and the lead 930 differs depending on portions of the solder 950. In such a case, there is a concern that the chip 920 is inclined when the solder 950 is solidified due to the aggregation of the solder and hence, there is a concern that the solder 950 has a small thickness portion locally thus giving rise to a drawback that the acquisition of a highly reliable semiconductor device is difficult. Such a problem occurs not only in the case where a solder is used but also in other cases where a conductive bonding material other than a solder is used.

In view of the above-mentioned circumstances, the present invention has been made to overcome the above-mentioned drawbacks, and it is an object of the present invention to provide a highly reliable semiconductor device.

Solution to Problem

[1] According to the present invention, there is provided a semiconductor device including: a substrate which has a front surface on which a wiring pattern having an electrode portion is formed; a chip which is disposed on the substrate and having a surface electrode formed on a surface of the chip on a side opposite to a substrate side; and a lead which has: a first electrode connecting portion disposed on the surface electrode and electrically connected to the surface electrode of the chip via a conductive bonding material, a second electrode connecting portion electrically connected to the electrode portion of the wiring pattern, and a current conductive portion which is connected to the first electrode connecting portion and the second electrode connecting portion and forms a current conductive path between the first electrode connecting portion and the second electrode connecting portion, wherein the lead further has a thermal shrinking stress equalizing structure which is disposed on a portion of an outer periphery of the first electrode connecting portion to which the current conductive portion is not connected as viewed in a plan view, and is configured to make a thermal shrinking stress applied to the conductive bonding material disposed between the first electrode connecting portion and the surface electrode equal. [2] In the semiconductor device of the present invention, it is preferable that the thermal shrinking stress equalizing structure have a bulging portion which bulges from the first electrode connecting portion on a side of the first electrode connecting portion opposite to a side of the first electrode connecting portion to which the current conductive portion is connected as viewed in a plan view. [3] In the semiconductor device of the present invention, it is preferable that the bulging portion bulge to a position symmetrical with the side to which the current conductive portion is connected with respect to the first electrode connecting portion. [4] In the semiconductor device of the present invention, it is preferable that the thermal shrinking stress equalizing structure have cutouts or holes which are formed in the lead at positions where the cutouts or the holes opposedly face each other with the first electrode connecting portion sandwiched therebetween. [5] In the semiconductor device of the present invention, it is preferable that the cutouts or the holes be disposed at positions symmetrical with respect to the surface electrode of the chip. [6] In the semiconductor device of the present invention, it is preferable that regions where the conductive bonding materials are bonded to the lead be symmetrical with respect to the center of the surface electrode as viewed in a cross section perpendicular to an outer periphery of the chip. [7] In the semiconductor device of the present invention, it is preferable that a heat resistance of the lead on one side of the center of the surface electrode and a heat resistance of the lead on the other side opposite to the one side be equal as viewed in the cross section perpendicular to the outer periphery of the chip. [8] In the semiconductor device of the present invention, it is preferable that the semiconductor device further include a pin terminal which is disposed on the lead in a penetrating manner, wherein one end portion of the pin terminal protrudes to an outside, and the other end portion of the pin terminal is connected to the wiring pattern.

Advantageous Effects of Invention

According to the semiconductor device of the present invention, the lead has the thermal shrinking stress equalizing structure which is disposed on the portion of the outer periphery of the first electrode connecting portion to which the current conductive portion is not connected as viewed in a plan view, and is configured to make a thermal shrinking stress applied to the conductive bonding material disposed between the first electrode connecting portion and the surface electrode equal. Accordingly, even when the substrate, the chip and the lead are heated at the time of bonding these members by the conductive bonding material, it is possible to make the surface area of the conductive bonding material which is brought into contact with the lead (including the front surface and the side surface of the lead) equal between one side of the first electrode connecting portion and the opposite side of the first electrode connecting portion as viewed in a plan view. Accordingly, the chip is minimally inclined at the time of solidifying the conductive bonding material (for example, due to the aggregation of the solder) and hence, the conductive bonding material can maintain a uniform thickness whereby it is possible to provide a highly reliable semiconductor device.

Further, according to the semiconductor device of the present invention, the lead has the thermal shrinking stress equalizing structure which is disposed on the portion of the outer periphery of the first electrode connecting portion to which the current conductive portion is not connected as viewed in a plan view and is configured to make a thermal shrinking stress applied to the conductive bonding material disposed between the first electrode connecting portion and the surface electrode equal. Accordingly, a heat resistance from a predetermined position of the lead to the chip can be made equal as viewed in a plan view between one side of the first electrode connecting portion and the other side of the first electrode connecting portion opposite to the one side. Accordingly, a heat transfer speed at the time of heating can be made equal and hence, the surface area of the conductive bonding material which is brought into contact with the lead can be made further equal.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A and FIG. 1B are views showing a semiconductor device 1 according to an embodiment 1. FIG. 1A is a plan view of the semiconductor device 1, and FIG. 1B is a cross-sectional view of the semiconductor device 1.

FIG. 2A and FIG. 2B are views showing a semiconductor device 2 according to an embodiment 2. FIG. 2A is a plan view of the semiconductor device 2, and FIG. 2B is a cross-sectional view of the semiconductor device 2. In FIG. 2A and FIG. 2B, symbol 34 a indicates a second electrode connecting portion.

FIG. 3 is a perspective view for describing a semiconductor device 3 according to an embodiment 3.

FIG. 4A and FIG. 4B are views for describing the semiconductor device 3 according to the embodiment 3. FIG. 4A is a view showing a state of the semiconductor device 3 before the semiconductor device 3 is sealed by a resin, and FIG. 4B is a view showing an equivalent circuit diagram of the semiconductor device 3. In FIG. 4A, symbols 30 d, 30 e, and 30 f indicate leads.

FIG. 5A, FIG. 5B and FIG. 5C are views for describing a thermal stress equalizing structure (bulging portion 41 a) in the embodiment 3. FIG. 5A is an enlarged plan view of a main part showing a region A surrounded by a chain line in FIG. 4A and FIG. 4B, FIG. 5B is a cross-sectional view taken along a line C-C in FIG. 5A, and FIG. 5C is a cross-sectional view taken along a line D-D in FIG. 5A.

FIG. 6A and FIG. 6B are views for describing a second thermal stress equalizing structure (cutouts 42 b, 42 c) in the embodiment 3. FIG. 6A is an enlarged plan view of a main part showing a region B surrounded by a chain line in FIG. 4A, and FIG. 6B is a cross-sectional view taken along a line E-E in FIG. 6A.

FIG. 7A and FIG. 7B are views for describing a conventional semiconductor device 900. FIG. 7A is a plan view of the semiconductor device 900, and FIG. 7B is a view showing a drawback that the semiconductor device 900 has. In FIG. 7A and FIG. 7B, symbol 924 indicates a gate electrode, and symbol 951 indicates a solder.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a semiconductor device according to the present invention is described based on an embodiment shown in drawings. The respective drawings are schematic views, and do not always strictly reflect the actual sizes.

Embodiment 1 1. Configuration of Semiconductor Device 1 According to Embodiment 1

As shown in FIG. 1A and FIG. 1B, a semiconductor device 1 according to the embodiment 1 includes a substrate 10, a chip 20, and a lead 30.

The substrate 10 is a substrate where a wiring pattern 11 is formed on one front surface of an insulating substrate 12. In the embodiment 1, as the substrate 10, a DCB substrate (direct copper bonding substrate) where a metal plate 13 for heat radiation is formed on a back surface of the substrate is used. However, any suitable substrate such as a printed circuit board may be also used.

The wiring pattern 11 has: a chip mounting portion 14 on which the chip 20 is mounted; and an electrode portion 15 which is connected to a source electrode 22 (surface electrode) of the chip 20 via the lead 30. The wiring pattern 11 is connected to a terminal for external connection not shown in the drawing.

The chip 20 is mounted on the chip mounting portion 14 of the substrate 10 via a conductive bonding material (solder 51). The chip 20 is a power MOSFET (metal-oxide-semiconductor field-effect transistor) having: a drain electrode formed on one surface (a surface on a substrate side); a source electrode 22 formed on the other surface (a surface on a side opposite to the substrate) and functioning as a surface electrode; and a gate electrode 24. The drain electrode is bonded to a chip mounting surface 16 via a conductive bonding material (solder 51), and the gate electrode 24 is connected to a predetermined portion of the wiring pattern 11 via a wire.

The lead 30 is a planar metal member which includes: a first electrode connecting portion 32 which is disposed on the source electrode 22 and is electrically connected to the source electrode 22 via a conductive bonding material (solder 50); a second electrode connecting portion 34 which is electrically connected to the electrode portion 15 of the wiring pattern 11; a current conductive portion 36 which is connected to the first electrode connecting portion 32 and the second electrode connecting portion 34, and forms a current conductive path between the first electrode connecting portion 32 and the second electrode connecting portion 34; and a thermal shrinking stress equalizing structure.

The first electrode connecting portion 32 is formed in an approximately rectangular shape, and the current conductive portions 36 are formed on two adjacently disposed sides (an upper side and a right side in FIG. 1A) of the rectangular shape. The second electrode connecting portion 34 is bonded to the electrode portion 15 via a conductive bonding material (not shown in the drawing). The thermal shrinking stress equalizing structure is described later.

The conductive bonding material is an alloy or a metal having conductivity and bonding property. In this embodiment, the solders 50, 51 are used as the conductive bonding material. Solders 50, 51 may be lead-free solder. Solders 50, 51 may be a conductive bonding material other than solder such as a conductive adhesive agent having a silver paste or silver nano particles.

As viewed in a cross section perpendicular to a side of the chip 20, regions with which the solder 50 and the lead 30 are brought into contact (the regions where solder is in a wet state) are disposed symmetrical with respect to the center of the source electrode 22 (a portion indicated by a chain line A-A shown in FIG. 1B).

The thermal shrinking stress equalizing structure is disposed on a portion of an outer periphery of the first electrode connecting portion 32 to which the current conductive portion 36 is not connected as viewed in a plan view and makes a thermal shrinking stress (see an arrow shown in FIG. 1B) applied to the solder 50 disposed between the first electrode connecting portion 32 and the source electrode 22 equal. The thermal shrinking stress equalizing structure has a bulging portion 41 which bulges from the first electrode connecting portion 32 on a side opposite to a side where the first electrode connecting portion 32 is connected to the current conductive portion 36. As viewed in a plan view, the bulging portion 41 bulges to a position where the bulging portion 41 is symmetrical with the current conductive portion 36 with respect to the first electrode connecting portion 32.

As shown in FIG. 1B, on a current conductive portion 36 side of the first electrode connecting portion 32, the solder 50 spreads by wetting along a surface of the lead 30 on a chip 20 side. On the other hand, a bulging portion 41 is also disposed on a side opposite to a current conductive portion 36 side and hence, the solder 50 spreads by wetting along a surface of the lead 30 on a chip 20 side. Accordingly, even when heat is applied in bonding the substrate 10, the chip 20 and the lead 30 by the solders 50, 51, as viewed in a plan view, it is possible to make a surface area of the solder 50 which is brought into contact with the lead 30 equal between one side of the first electrode connecting portion 32 (current conductive portion 36 side) and a side opposite to the one side of the first electrode connecting portion 32 (bulging portion 41 side).

The thermal shrinking stress equalizing structure is configured such that the difference between a transfer speed of heat transferred to the solder 50 from a side of the first electrode connecting portion 32 which is connected to the current conductive portion 36 and a transfer speed of heat transferred to the solder 50 from a bulging portion 41 side of the first electrode connecting portion 32 is reduced.

In other words, as viewed in a cross section perpendicular to an outer periphery of the chip 20, the thermal shrinking stress equalizing structure is configured such that a heat resistance of the lead 30 on one side from the center of the source electrode 22 and a heat resistance of the lead on the other side from the center of the source electrode 22 become equal.

Accordingly, the thermal shrinking stress equalizing structure is configured to make the solder 50 uniformly spread by wetting by making heat transferred to the solder 50 between the source electrode 22 and the lead 30 equal.

2. Advantageous Effects of Semiconductor Device 1 According to Embodiment 1

According to the semiconductor device 1 of the embodiment 1, the lead 30 has the thermal shrinking stress equalizing structure which is disposed on the portion of the outer periphery of the first electrode connecting portion 32 to which the current conductive portion 36 is not connected as viewed in a plan view and makes a thermal shrinking stress applied to the solder 50 disposed between the first electrode connecting portion 32 and the source electrode 22 as viewed in a plan view equal. Accordingly, even when the substrate 10, the chip 20 and the lead 30 are heated at the time of bonding these members by the solder 50, the surface area of the solder 50 which is brought into contact with the lead 30 (including the front surface and the side surface of the lead) can be made equal between one side of the first electrode connecting portion 32 and the side opposite to the one side of the first electrode connecting portion 32 as viewed in a plan view. Accordingly, the chip 20 is minimally inclined at the time of solidifying a conductive bonding material (for example, due to the aggregation of the solder 50) and hence, the solder 50 can maintain a uniform thickness whereby it is possible to provide a highly reliable semiconductor device.

Further, according to the semiconductor device 1 of the embodiment 1, the lead 30 has the thermal shrinking stress equalizing structure which is disposed on the portion of the outer periphery of the first electrode connecting portion 32 to which the current conductive portion 36 is not connected, as viewed in a plan view, and makes a thermal shrinking stress applied to the solder 50 disposed between the first electrode connecting portion 32 and the source electrode 22 equal. Accordingly, it is possible to make a heat resistance from a predetermined position of the lead to the chip 20 equal between one side of the first electrode connecting portion 32 and the other side of the first electrode connecting portion 32 opposite to the one side as viewed in a plan view. Accordingly, a heat transfer speed at the time of heating can be made equal between the one side and the other side of the first electrode connecting portion 32 and hence, a surface area of the solder 50 which is brought into contact with the lead 30 can be made further equal between the one side and the other side of the first electrode connecting portion 32.

According to the semiconductor device 1 of the embodiment 1, the thermal shrinking stress equalizing structure has the bulging portion 41 which bulges from the first electrode connecting portion 32 on a side of the first electrode connecting portion 32 opposite to a side of the first electrode connecting portion 32 which is connected to the current conductive portion 36 as viewed in a plan view. Accordingly, the solder 50 spreads by wetting along the surface of the lead 30 on a chip 20 side on both a current conductive portion 36 side of the first electrode connecting portion 32 and a bulging portion 41 side of the first electrode connecting portion 32 opposite to the current conductive portion 36 side. Accordingly, the surface area (including the front surface and the side surface of the lead) of the solder 50 which is brought into contact with the lead 30 can be made equal between one side and the side opposite to the one side of the first electrode connecting portion 32 as viewed in a plan view.

Further, according to the semiconductor device 1 of the embodiment 1, the bulging portion 41 bulges to a position symmetrical with a side where the current conductive portion 36 is connected to the first electrode connecting portion 32 with respect to the first electrode connecting portion 32. Accordingly, a difference between a transfer speed of heat transferred to the solder 50 from the side to which the current conductive portion 36 is connected and a transfer speed of heat transferred to the solder 50 from the bulging portion 41 side becomes smaller. Accordingly, a difference in a thermal shrinking stress applied to the solder 50 between the side of the first electrode connecting portion 32 to which the current conductive portion 36 is connected and the side of the first electrode connecting portion 32 opposite to such a side becomes smaller and hence, the chip 20 is minimally inclined when the solder 50 is solidified.

Further, according to the semiconductor device 1 of the embodiment 1, regions where the solder 50 is disposed with respect to the center of the source electrode 22 are symmetrical. Accordingly, the chip 20 is minimally inclined and hence, the solder 50 can maintain a uniform thickness whereby it is possible to provide a more reliable semiconductor device.

Further, according to the semiconductor device 1 of the embodiment 1, as viewed in a cross section perpendicular to the outer periphery of the chip 20, a heat resistance of the lead 30 on one side from the center of the source electrode 22 and a heat resistance of the lead 30 on the other side from the center of the source electrode 22 become equal. Accordingly, a thermal shrinking stress applied to the solder 50 becomes also symmetrical between on one side from the center of the source electrode 22 and on the other side from the center of the source electrode 22 and hence, the occurrence of the inclination of the chip 20 can be more effectively prevented.

Embodiment 2

A semiconductor device 2 according to the embodiment 2 basically has substantially the same configuration as the semiconductor device 1 according to the embodiment 1. However, the semiconductor device 2 according to the embodiment 2 differs from the semiconductor device 1 according to the embodiment 1 with respect to the configuration of a thermal shrinking stress equalizing structure. That is, in the semiconductor device 2 according to the embodiment 2, the thermal shrinking stress equalizing structure has cutouts 42 formed in a lead 30 a at positions which opposedly face each other with a first electrode connecting portion 32 a sandwiched therebetween (see FIG. 2A and FIG. 2B).

In the lead 30 a of the embodiment 2, current conductive portions 36 a are formed on two opposedly facing sides of a rectangular first electrode connecting portion 32 a (see an upper side and a lower side of FIG. 2A). The cutouts 42 are formed on portions of the lead 30 a where the current conductive portion 36 a is not connected to the first electrode connecting portion 32 a, that is, sides which are disposed adjacently to the respective current conductive portions 36 a (a right side and a left side in FIG. 2A). The cutouts 42 are respectively formed in a triangular shape having a vertex toward a chip 20 side. The cutouts 42 are disposed at positions symmetrical with respect to a source electrode 22 of the chip 20.

As shown in FIG. 2B, in both two opposedly facing sides of the first electrode connecting portion 32 a where the cutouts 42 are formed, a solder 50 spreads by wetting along the front surface of the lead 30 a on a chip 20 side, and the solder 50 creeps along side surfaces of the lead 30 a (side surfaces of the cutouts 42). Accordingly, even when heat is applied in bonding a substrate 10, the chip 20 and the lead 30 a to each other by the solder 50, a surface area of the solder 50 which is brought into contact with the lead 30 a (including a front surface and side surfaces of the lead 30 a) as viewed in a plan view can be made equal between one side and the other side of the first electrode connecting portion 32 a (at two opposedly facing sides where the cutouts 42 are formed). As a result, a thermal shrinking stress applied to the solder 50 can be made equal.

In this manner, the semiconductor device 2 according to the embodiment 2 differs from the semiconductor device 1 according to the embodiment 1 with respect to the configuration of the thermal shrinking stress equalizing structure. However, in the same manner as the case of the semiconductor device 1 according to the embodiment 1, according to the semiconductor device 2 of the embodiment 2, the lead 30 a has a thermal shrinking stress equalizing structure which is disposed on portions of an outer periphery of the first electrode connecting portion 32 a to which the current conductive portions 36 a are not connected and makes a thermal shrinking stress applied to the solder 50 disposed between the first electrode connecting portion 32 a and the source electrode 22 equal. Accordingly, even when heat is applied in bonding a substrate 10, the chip 20 and the lead 30 a to each other by the solder 50 and a solder 51, the surface area of the solder 50 which is brought into contact with the lead 30 a (including the front surface and the side surfaces of the lead 30 a) as viewed in a plan view can be made equal between one side and the other side of the first electrode connecting portion 32 a. Accordingly, the chip 20 is minimally inclined at the time of solidifying a conductive bonding material (for example, due to the aggregation of the solder 50) and hence, the solder 50 can maintain a uniform thickness whereby it is possible to provide a highly reliable semiconductor device.

Further, according to the semiconductor device 2 of the embodiment 2, the thermal shrinking stress equalizing structure has the cutouts 42 formed in the lead 30 a at the positions which opposedly face each other with the first electrode connecting portion 32 sandwiched therebetween. Accordingly, in both two opposedly facing sides of the first electrode connecting portion 32 a where the cutouts 42 are formed, the solder 50 spreads by wetting along a front surface of the lead 30 a on a chip 20 side, and the solder 50 creeps along side surfaces of the lead 30 a (side surfaces of the cutouts 42). Accordingly, even when heat is applied in bonding the substrate 10, the chip 20 and the lead 30 to each other by the solder, a surface area of the solder 50 which is brought into contact with the lead 30 a (including the front surface and the side surfaces of the lead 30 a) as viewed in a plan view can be made equal between one side and the other side of the first electrode connecting portion 32 a (two opposedly facing sides where the cutouts 42 are formed). As a result, a thermal shrinking stress applied to the solder 50 can be made equal between one side and the other side of the first electrode connecting portion 32 a.

According to the semiconductor device 2 of the embodiment 2, the cutouts 42 are disposed at positions symmetrical with respect to a source electrode 22 of the chip 20 and hence, the surface area of the solder 50 which is brought into contact with the lead 30 a (including the front surface and the side surfaces of the lead 30 a) as viewed in a plan view can be made equal with more certainty between one side and the other side of the first electrode connecting portions 32 a (two opposedly facing sides where the cutouts 42 are formed).

The semiconductor device 2 according to the embodiment has substantially the same configuration as the semiconductor device 1 according to the embodiment 1 except for the configurations of the thermal shrinking stress equalizing structure. Accordingly, the semiconductor device 2 according to the embodiment 2 acquires the corresponding advantageous effects found amongst all advantageous effects which the semiconductor device 1 according to the embodiment 1 acquires.

Embodiment 3

A semiconductor device 3 according to the embodiment 3 basically has substantially the same configuration as the semiconductor device 1 according to the embodiment 1. However, the semiconductor device 3 according to the embodiment 3 differs from the semiconductor device 1 according to the embodiment 1 with respect to points that the semiconductor device 3 according to the embodiment 3 has two chips as chips, and also has pin terminals.

The semiconductor device 3 according to the embodiment 3 is not a semiconductor device where terminals are provided at side surfaces of the semiconductor device sealed by a resin but, as shown in FIG. 3, is a semiconductor device provided with terminals (pin terminals) protruding from an upper surface of the semiconductor device which is sealed by a resin.

The pin terminals are disposed on a lead in a penetrating manner, wherein one end portion of the pin terminal protrudes to the outside from a mold resin 70, and the other end portion is connected to a wiring pattern. The pin terminal is an elongated circular columnar conductive pin having a flange portion which is a large diameter portion at a center portion (see FIG. 3 and FIG. 4A). The pin terminal is used as a terminal for external connection, and also is used as a member which connects the lead and the wiring pattern to each other.

As shown in FIG. 3 and FIG. 4A and FIG. 4B, the pin terminal includes: a pin terminal 60 g which is connected to a gate electrode 24 a of a chip 20 a; a pin terminal 60 s which is connected to a source electrode 22 a of the chip 20 a; a pin terminal 61 s which is connected to the source electrode 22 a of the chip 20 a and a drain electrode of a chip 20 b; two pin terminals 60 d which are connected to a drain electrode of the chip 20 a; a pin terminal 61 g which is connected to a gate electrode 24 b of the chip 20 b; and pin terminals 62 s,63 s which are connected to a source electrode 22 b of the chip 20 b.

As shown in FIG. 4A and FIG. 4B, the semiconductor device 3 according to the embodiment 3 has two chips 20 a, 20 b as the chips. Each of these two chips has a drain electrode (not shown in a drawing) on a wiring pattern 11 (chip mounting surface) side of a substrate 10, and has the source electrodes 22 a, 22 b and the gate electrodes 24 a, 24 b on a side opposite to the substrate 10. With such a configuration, a circuit where two switching elements are connected in series is formed by two chips 20 a, 20 b, the wiring pattern 11 of the substrate 10, the leads 30 b, 30 c and the respective pin terminals (see FIG. 4B).

As shown in FIG. 4A, the lead 30 b includes: a first electrode connecting portion 32 b disposed on the source electrode 22 a of the chip 20 a and electrically connected to the source electrode 22 a of the chip 20 a via a solder 50; a second electrode connecting portion 34 b connected to an electrode portion of the wiring pattern 11 via the pin terminal 60 s; a second electrode connecting portion 34 c connected to the electrode portion of the wiring pattern 11 via the pin terminal 61 s; a current conductive portion 36 b connected to the first electrode connecting portion 32 b and the second electrode connecting portion 34 b and forming a current conductive path between the first electrode connecting portion 32 b and the second electrode connecting portion 34 b; and a current conductive portion 36 c connected to the first electrode connecting portion 32 b and the second electrode connecting portion 34 c and forming a current conductive path between the first electrode connecting portion 32 b and the second electrode connecting portion 34 c.

As shown in FIG. 4A and FIG. 4B and FIG. 5A, FIG. 5B and FIG. 5C, the lead 30 b includes a bulging portion 41 a which forms a thermal shrinking stress equalizing structure at a side (portion) of an outer periphery of the first electrode connecting portion 32 b which is the side opposite to a current conductive portion 36 b side (a portion on a lower side of FIG. 4A and FIG. 5A) which is not connected to the current conductive portions 36 b, 36 c (see FIG. 5A).

The current conductive portion 36 b is connected to the first electrode connecting portion 32 b at a position where the current conductive portion 36 b is displaced from the source electrode 22. That is, the current conductive portion 36 b is connected to the first electrode connecting portion 32 b such that the source electrode 22 a is displaced from a region extending to a source electrode side. The bulging portion 41 a is disposed at a position where the bulging portion 41 a is symmetrical with the current conductive portion 36 b with respect to the first electrode connecting portion 32 b.

As shown in FIG. 5B, on a current conductive portion 36 b side of the first electrode connecting portion 32 b, the solder 50 spreads by wetting along a surface of the lead 30 b on a chip 20 a side. On the other hand, the bulging portion 41 a is also disposed on a side opposite to a current conductive portion 36 b side and hence, the solder 50 spreads by wetting along a surface of the lead 30 b on a chip 20 a side. Accordingly, even when heat is applied in bonding the substrate 10, the chip 20 b and the lead 30 b by the solder 50, it is possible to make a surface area of the solder 50 which is brought into contact with the lead 30 b equal between one side (current conductive portion 36 b side) and a side opposite to the one side (bulging portion 41 a side) of the first electrode connecting portion 32 b as viewed in a plan view.

In the lead 30 b, a hole 43 a is formed in the current conductive portion 36 b, and a cutout 42 a which corresponds to the hole 43 a is formed in the current conductive portion 36 b at positions which opposedly face each other with the source electrode 22 sandwiched therebetween. The formation of the hole in the current conductive portion 36 b is not desirable since the hole obstructs the conduction of an electric current. However, as in the case of this embodiment, when a sufficient conduction of an electric current is ensured by increasing a cross-sectional area of the current conducive portion 36 b by increasing a width of the current conductive portion 36 b, it is possible to prevent the occurrence of a difference in a thermal shrinking stress applied to a conductive bonding material by forming the cutout or the hole.

That is, as shown in FIG. 5C, in both two opposedly facing sides of the first electrode connecting portion 32 b where the cutout 42 a and the hole 43 a are formed, a solder 50 spreads by wetting along surfaces of the lead 30 b on a chip 20 a side, and the solder 50 creeps along side surfaces of the lead 30 b (a side surface of the cutout 42 a and a side surface of the hole 43 a). Accordingly, even when heat is applied in bonding a substrate 10, the chip 20 a and the lead 30 b to each other by the solder 50, a surface area of the solder 50 which is brought into contact with the lead 30 b (including a front surface and side surfaces of the lead 30) as viewed in a plan view can be made equal between one side of the first electrode connecting portion 32 b and the other side (the side where the cutout 42 a is formed and the side where the hole 43 a which faces the cutout 42 a is formed) of the first electrode connecting portion 32 b.

As shown in FIG. 4A and FIG. 4B and FIG. 6A and FIG. 6B, the lead 30 c includes: a first electrode connecting portion 32 c disposed on the source electrode 22 b of the chip 20 a and electrically connected to the source electrode 22 b of the chip 20 b via the solder 50; a second electrode connecting portion 34 d connected to an electrode portion of the wiring pattern 11 via the pin terminal 62 s (see FIG. 4A); a second electrode connecting portion 34 e connected to the electrode portion of the wiring pattern 11 via the pin terminal 63 s (see FIG. 4A); a current conductive portion 36 d connected to the first electrode connecting portion 32 c and the second electrode connecting portion 34 d, and forming a current conductive path between the first electrode conductive portion 32 c and the second electrode connecting portion 34 d; and a current conductive portion 36 e connected to the first electrode connecting portion 32 c and the second electrode connecting portion 34 e and forming a current conductive path between the first electrode connecting portion 32 c and the second electrode connecting portion 34 e.

The current conductive portions 36 d, 36 e are formed on both two opposedly facing sides (an upper side and a lower side in FIG. 4A and FIG. 4B and FIG. 6A and FIG. 6B) of a rectangular shape of the first electrode connecting portion 32. Cutouts 42 b, 42 c are formed on a portion to which the current conductive portions are not connected, that is, sides disposed adjacently to the respective current conductive portions 36 d, 36 e in a state where each cutout 42 b, 42 c is formed in a pentagonal shape having a vertex toward a chip side. The cutouts 42 b, 42 c are disposed at positions symmetrical with respect to the source electrode 22 b of the chip 20 b. However, a thickness and a length of the cutouts 42 b, 42 c are taken into account such that balancing of an area (volume) of a portion which is not cut out is ensured.

As shown in FIG. 6B, in both two opposedly facing sides of the first electrode connecting portion 32 c where the cutouts 42 b, 42 c are formed, the solder 50 spreads by wetting along a front surface of the lead 30 c on a chip 20 b side, and the solder 50 creeps along side surfaces of the lead 30 c (side surfaces of the cutouts 42 b, 42 c). Accordingly, even when heat is applied in bonding a substrate, the chip 20 b and the lead 30 c to each other by the solder 50, a surface area of the solder 50 which is brought into contact with the lead 30 c (including a front surface and side surfaces of the lead 30 c) as viewed in a plan view can be made equal between one side and the other side of the first electrode connecting portion 32 c (two opposedly facing sides on which the cutouts 42 b, 42 c are formed). As a result, a thermal shrinking stress applied to the solder 50 can be made equal.

In this manner, the semiconductor device 3 according to the embodiment 3 differs from the semiconductor device according to the embodiment 1 with respect to a point that the semiconductor device 3 according to the embodiment 3 includes two chips as the chips and the pin terminals. However, in the same manner as the case of the semiconductor device 1 according to the embodiment 1 and the semiconductor device 2 according to the embodiment 2, the leads 30 b, 30 c have the thermal shrinking stress equalizing structure which is disposed on portions of outer peripheries of the first electrode connecting portions 32 b, 32 c to which the current conductive portion is not connected and make a thermal shrinking stress applied to the solder 50 disposed between the first electrode connecting portions 32 b, 32 c and the source electrodes 22 b, 22 c equal. Accordingly, surface areas of the solders 50 which are brought into contact with the leads 30 b, 30 c (including front surfaces and side surfaces of the leads 30 b, 30 c) as viewed in a plan view can be made equal between one side and the other side of the first electrode connecting portion 32 b, 32 c. Accordingly, the chips 20 a, 20 b are minimally inclined when a conductive bonding material is solidified (for example, due to the aggregation of the solder 50) and hence, the solder 50 can maintain a uniform thickness whereby it is possible to provide highly reliable semiconductor devices.

The semiconductor device 3 according to the embodiment 3 further includes the pin terminals which are disposed on the leads 30 b, 30 c in a penetrating manner, wherein one end portion of the pin terminal protrudes to the outside and the other end portion of the pin terminal is connected to the wiring pattern 11. With such a configuration, even in a case where it is difficult for the leads 30 b, 30 c to realize the self-alignment due to fixing of the leads 30 b, 30 c to the substrate 10 by way of the pin terminals 60 s, 61 s, 62 s, 63 s, a difference minimally occurs in a thermal shrinking stress applied to the solder 50 and hence, offsetting of the conductive bonding material minimally Occurs. Accordingly, the chips 20 b, 20 c are minimally inclined when the conductive bonding material is solidified (due to the aggregation of the solder) and hence, a thickness of the conductive bonding material can maintain a uniform thickness whereby it is possible to provide a highly reliable semiconductor device.

The semiconductor device 3 according to the embodiment has substantially the same configuration as the semiconductor device 1 according to the embodiment 1 with respect to the points other than the point that the semiconductor device 3 according to the embodiment 3 includes two chips as the chips and also includes the pin terminals. Accordingly, the semiconductor device 3 according to the embodiment 3 acquires the corresponding advantageous effects found amongst all advantageous effects which the semiconductor device 1 according to the embodiment 1 acquires.

Although the present invention has been described based on the above-mentioned embodiments, the present invention is not limited to the above-mentioned embodiments. The present invention can be carried out in various modes without departing from the gist of the present invention, and the following modifications are also conceivable, for example.

(1) In the above-mentioned embodiments, the materials, the shapes, the positions, the sizes and the like are described for an exemplifying purpose, and these can be changed within a scope that the advantageous effects of the present invention are not impaired. (2) In the above-mentioned embodiments 2 and 3, the cutouts are formed as the thermal shrinking stress equalizing structure. However, the present invention is not limited to such a structure. Holes may be formed as the thermal shrinking stress equalizing structure. (3) In the above-mentioned embodiments 2 and 3, a triangular or pentagonal cutout is formed as the cutout. However, the present invention is not limited to such a cutout. As such a cutout, a cutout having a rectangular shape, a circular shape or other suitable shape may be formed. (4) In the above-mentioned respective embodiments, a chip which is a MOSFET is used as the chip. However, the present invention is not limited to such a chip. As the chip, an IGBT, a thyristor, a diode, or other suitable element may be also used. Further, as a material for forming the chip, silicon, SiC, GaN or a suitable material may be also used. (5) In the above-mentioned respective embodiments, as the chip, the so-called vertical semiconductor device which has the source electrode on one surface of the chip and the drain electrode on the other surface of the chip and where a main current flows vertically is used. However, the present invention is not limited to such a vertical semiconductor device. As the chip, a so-called lateral semiconductor device which has a source electrode and a drain electrode on one surface of the chip and where a main current flows laterally may be used. 

1. A semiconductor device comprising: a substrate which has a front surface on which a wiring pattern having an electrode portion is formed; a chip which is disposed on the substrate and having a surface electrode formed on a surface of the chip on a side opposite to a substrate side; and a lead which has: a first electrode connecting portion disposed on the surface electrode and electrically connected to the surface electrode of the chip via a conductive bonding material, a second electrode connecting portion electrically connected to the electrode portion of the wiring pattern, and a current conductive portion which is connected to the first electrode connecting portion and the second electrode connecting portion and forms a current conductive path between the first electrode connecting portion and the second electrode connecting portion, wherein the lead further has a thermal shrinking stress equalizing structure which is disposed on a portion of an outer periphery of the first electrode connecting portion to which the current conductive portion is not connected as viewed in a plan view, and is configured to make a thermal shrinking stress applied to the conductive bonding material disposed between the first electrode connecting portion and the surface electrode equal, and the thermal shrinking stress equalizing structure has cutouts or holes formed in the lead at positions which opposedly face each other with the first electrode connecting portion sandwiched therebetween.
 2. The semiconductor device according to claim 1, wherein the thermal shrinking stress equalizing structure has a bulging portion which bulges from the first electrode connecting portion on a side of the first electrode connecting portion opposite to a side of the first electrode connecting portion to which the current conductive portion is connected as viewed in a plan view.
 3. The semiconductor device according to claim 2, wherein the bulging portion bulges to a position symmetrical with the side to which the current conductive portion is connected with respect to the first electrode connecting portion.
 4. (canceled)
 5. The semiconductor device according to claim 1, wherein the cutouts or the holes are disposed at positions symmetrical with respect to the surface electrode of the chip.
 6. The semiconductor device according to claim 1, wherein regions where the conductive bonding materials are bonded to the lead are symmetrical with respect to the center of the surface electrode as viewed in a cross section perpendicular to an outer periphery of the chip.
 7. The semiconductor device according to claim 1, wherein a heat resistance of the lead on one side of the center of the surface electrode and a heat resistance of the lead on other side opposite to the one side are equal as viewed in a cross section perpendicular to the outer periphery of the chip.
 8. The semiconductor device according to claim 1 further comprising a pin terminal which is disposed on the lead in a penetrating manner, wherein one end portion of the pin terminal protrudes to an outside, and other end portion of the pin terminal is connected to the wiring pattern.
 9. A semiconductor device comprising: a substrate which has a front surface on which a wiring pattern having an electrode portion is formed; a chip which is disposed on the substrate and having a surface electrode formed on a surface of the chip on a side opposite to a substrate side; and a lead which has: a first electrode connecting portion disposed on the surface electrode and electrically connected to the surface electrode of the chip via a conductive bonding material, a second electrode connecting portion electrically connected to the electrode portion of the wiring pattern, and a current conductive portion which is connected to the first electrode connecting portion and the second electrode connecting portion and forms a current conductive portion which forms a current conductive path between the first electrode connecting portion and the second electrode connecting portion, wherein the lead further has a thermal shrinking stress equalizing structure which is disposed on a portion of an outer periphery of the first electrode connecting portion to which the current conductive portion is not connected as viewed in a plan view, and is configured to make a thermal shrinking stress applied to the conductive bonding material disposed between the first electrode connecting portion and the surface electrode equal, and the semiconductor device further comprises a pin terminal which is disposed on the lead in a penetrating manner, one end portion of the pin terminal protrudes to an outside, and other end portion of the pin terminal is connected to the wiring pattern.
 10. The semiconductor device according to claim 9, wherein the thermal shrinking stress equalizing structure has a bulging portion which bulges from the first electrode connecting portion on a side of the first electrode connecting portion opposite to a side of the first electrode connecting portion to which the current conductive portion is connected as viewed in a plan view.
 11. The semiconductor device according to claim 10, wherein the bulging portion bulges to a position symmetrical with the side to which the current conductive portion is connected with respect to the first electrode connecting portion.
 12. The semiconductor device according to claim 9, wherein regions where the conductive bonding materials are bonded to the lead are symmetrical with respect to the center of the surface electrode as viewed in a cross section perpendicular to an outer periphery of the chip.
 13. The semiconductor device according to claim 9, wherein a heat resistance of the lead on one side of the center of the surface electrode and a heat resistance of the lead on other side opposite to the one side are equal as viewed in a cross section perpendicular to the outer periphery of the chip. 